RUO · Research Use Only⚠ Cancer Concern⚠ WADA BannedFor Energy+2 more
IGF-1 LR3
A long-acting analog of insulin-like growth factor 1 with an arginine substitution and an N-terminal extension that blunts IGF binding-protein affinity. We read all 22 studies. The protocol is below.
Updated 03 May 2026Read 11 minEvidence ●○○○○Citations 22
Free — puts IGF-1 LR3 on your decision board.
The IGF-1 LR3 Report · $19
Everything you need to start: dose, sourcing, safety, our verdict.
One purchase · yours forever
Built from 22 cited studies.
Read this if
- you're an IFBB-Pro-adjacent bodybuilder and you want the technical read before you run it
- you graduated from MK-677 and want a more direct effect
- you've heard the hypoglycemia stories and want to know what's actually true
- you're trying to tell the difference between native IGF-1 (Increlex / mecasermin) and the LR3 analog — they are not the same molecule
Skip this if
- **you have a personal or family history of breast, prostate, or colorectal cancer** — the IGF-1 epidemiology (Renehan Lancet 2004) is real and this is the wrong molecule for you
- you compete in a tested sport — WADA-banned
- you're not okay with acute hypoglycemia risk and the supply-chain identity question that comes with LR3 (vials labeled LR3 frequently ship as plain IGF-1)
The 4 ways you can buy IGF-1 LR3
Full breakdown ↓Brand
✗
No FDA approval
Compounded 503A
✗
Not available
LR3 is not a recognized therapeutic; no 503A pathway.
RUO (research-only)
✓
Sold for research only
$80–$180/mo
Entire off-label channel; purity, identity, endotoxin status unverified.
Gray market
✓
Illegal to import for huma…
$30–$70/mo at 50mcg/d
Active gray channel; LR3 identity verification is the recurring failure mode (often shipped as pla…
Click any lane for the full Sourcing breakdown. Prices and lane availability vary by molecule — this is the per-peptide snapshot, not a generic table.
First 90 days · IGF-1 LR3
What we'd actually do
Weeks 1–2
Sleep depth shifts within days for the GH-secretagogue class (CJC, ipamorelin, sermorelin, hexarelin). If sleep hasn't deepened by week 2, the rest of the protocol probably won't move either.
Weeks 4–8
Subjective recovery and energy improvements. Body composition shifts modestly — slight muscle gain, slight fat loss if diet allows.
Week 12 — decide
Bloodwork: IGF-1 is the objective check. If IGF-1 hasn't moved, the protocol isn't working at this dose. Side effect bookkeeping: water retention, joint stiffness, any glucose changes.
Quit if
- IGF-1 climbs above ~300 ng/mL (cancer-risk territory at the upper end).
- Significant water retention or new carpal-tunnel-style symptoms.
- New or worsening insulin resistance (fasting glucose creep).
- 12 weeks with no IGF-1 movement and no subjective change.
Identity
What it is.
LR3 is a synthetic analog of insulin-like growth factor 1 — the same molecule the liver produces in response to growth hormone and that mediates most of GH's downstream effects. The "LR3" stands for Long R3: the molecule has been modified with an extra 13 amino acids on the N-terminus and a single substitution that makes it resistant to binding by IGF-binding proteins (IGFBPs).
That modification is the entire point. Native in circulation is mostly bound to IGFBPs and is biologically silent. LR3 escapes that buffer system and stays free, which extends its from roughly 10 minutes (native IGF-1) to several hours and dramatically increases its bioactivity per unit dose.
It has no FDA approval for human use. Sold as a laboratory reagent and as a research chemical (RUO) in the US, primarily marketed to bodybuilders. WADA-banned in and out of competition.
TL;DR
TL;DR. 30-second version.
The compressed verdict — what IGF-1 LR3 actually is, what the human evidence shows, and the watch-for in three bullets. Locked.
Get the report · $19 ↓Mechanism
Mechanism.
Mechanism · in the IGF-1 LR3 report
How the molecule actually works — receptor profile, downstream signaling, what to expect mechanistically.
Get the report · $19 ↓Evidence
Evidence. What we actually know in humans.
Evidence · in the IGF-1 LR3 report
The trial breakdown — phase, n, primary endpoint, who funded, what hit, what didn't.
Get the report · $19 ↓Human-Evidence Factbox
Dose
Dose. The actual protocol.
Dose · in the IGF-1 LR3 report
The specific protocol — dose, titration schedule, cycle pattern, frequency, route.
We read 22 studies to write this report.
Get the report · $19 ↓Sourcing
Sourcing. Where the cohort actually buys.
Sourcing · in the IGF-1 LR3 report
Sourcing breakdown — vendor methodology, red flags, our published test results, COA checklist.
We read 22 studies to write this report.
Get the report · $19 ↓Safety
Safety. Side effects.
Safety · in the IGF-1 LR3 report
The watch-for list — contraindications, drug interactions, monitoring labs, when to stop.
Get the report · $19 ↓Editorial Position
Editorial position.
Editorial Position · in the IGF-1 LR3 report
Our editorial position — explicit yes / no / depends, with the reasoning behind it.
Get the report · $19 ↓Citations
Citations.
- 01Lu Z, et al. Recombinant expression of IGF-1 and LR3 IGF-1 fused with xylanase in Pichia pastoris. Applied microbiology and biotechnology. 2023;107(14):4543-4551. PMID: 37261455.
- 02White A, et al. IGF-1 LR3 does not promote growth in late-gestation growth-restricted fetal sheep. American journal of physiology. Endocrinology and metabolism. 2025;328(1):E116-E125. PMID: 39679943.
- 03White A, et al. Attenuated glucose-stimulated insulin secretion during an acute IGF-1 LR3 infusion into fetal sheep does not persist in isolated islets. Journal of developmental origins of health and disease. 2023;14(3):353-361. PMID: 37114757.
- 04Engel MG, et al. Intranasal long R3 insulin-like growth factor-1 treatment promotes amyloid plaque remodeling in cerebral cortex but fails to preserve cognitive function in male 5XFAD mice. Journal of Alzheimer's disease : JAD. 2025;103(1):113-126. PMID: 39610283.
- 05Stremming J, et al. Sheep recombinant IGF-1 promotes organ-specific growth in fetal sheep. Frontiers in physiology. 2022;13:954948. PMID: 36091374.
+Show all 22 citationsShow fewer citations
- 06Hill RA, et al. Action of long(R3)-insulin-like growth factor-1 on protein metabolism in beef heifers. Domestic animal endocrinology. 1999;16(4):219-29. PMID: 10370861.
- 07Jonker SS, et al. Coronary vascular growth matches IGF-1-stimulated cardiac growth in fetal sheep. FASEB journal : official publication of the Federation of American Societies for Experimental Biology. 2020;34(8):10041-10055. PMID: 32573852.
- 08Yavuz E, et al. Revolutionary decellularized Alstroemeria stem-based nerve conduit integrated with GelMA and controlled IGF-1 LR3 release for enhanced rat sciatic nerve regeneration. International journal of biological macromolecules. 2025;329(Pt 2):147888. PMID: 41015370.
- 09Stremming J, et al. IGF-1 infusion to fetal sheep increases organ growth but not by stimulating nutrient transfer to the fetus. American journal of physiology. Endocrinology and metabolism. 2021;320(3):E527-E538. PMID: 33427051.
- 10White A, et al. Reduced glucose-stimulated insulin secretion following a 1-wk IGF-1 infusion in late gestation fetal sheep is due to an intrinsic islet defect. American journal of physiology. Endocrinology and metabolism. 2021;320(6):E1138-E1147. PMID: 33938236.
- 11von der Thüsen JH, et al. IGF-1 has plaque-stabilizing effects in atherosclerosis by altering vascular smooth muscle cell phenotype. The American journal of pathology. 2011;178(2):924-34. PMID: 21281823.
- 12Salvi R, et al. N-Linked Glycosylation in Chinese Hamster Ovary Cells Is Critical for Insulin-like Growth Factor 1 Signaling. International journal of molecular sciences. 2022;23(23). PMID: 36499281.
- 13Richards RG, et al. Insulin-like growth factor-1 (IGF-1) receptor-insulin receptor substrate complexes in the uterus. Altered signaling response to estradiol in the IGF-1(m/m) mouse. The Journal of biological chemistry. 1998;273(19):11962-9. PMID: 9565625.
- 14Sundgren NC, et al. Extracellular signal-regulated kinase and phosphoinositol-3 kinase mediate IGF-1 induced proliferation of fetal sheep cardiomyocytes. American journal of physiology. Regulatory, integrative and comparative physiology. 2003;285(6):R1481-9. PMID: 12947030.
- 15McTavish H, et al. Novel insulin-like growth factor-methotrexate covalent conjugate inhibits tumor growth in vivo at lower dosage than methotrexate alone. Translational research : the journal of laboratory and clinical medicine. 2009;153(6):275-82. PMID: 19446281.
- 16Reiter BC, et al. Epidermal growth factor receptor is required for estradiol-stimulated bovine satellite cell proliferation. Domestic animal endocrinology. 2014;48:48-55. PMID: 24906928.
- 17Long E, et al. Involvement of insulin-like growth factor-1 and its binding proteins in proliferation and differentiation of murine bone marrow-derived macrophage precursors. Endocrine. 1998;9(2):185-92. PMID: 9867252.
- 18Shen Z, et al. Na+ transport across rumen epithelium of hay-fed sheep is acutely stimulated by the peptide IGF-1 in vitro. Experimental physiology. 2012;97(4):497-505. PMID: 22227200.
- 19Glister C, et al. Oocyte-mediated suppression of follicle-stimulating hormone- and insulin-like growth factor-induced secretion of steroids and inhibin-related proteins by bovine granulosa cells in vitro: possible role of transforming growth factor alpha. Biology of reproduction. 2003;68(3):758-65. PMID: 12604623.
- 20Lovell TM, et al. Modulatory effects of gonadotrophins and insulin-like growth factor on the secretion of inhibin A and progesterone by granulosa cells from chicken preovulatory (F1-F3) follicles. Reproduction (Cambridge, England). 2002;123(2):291-300. PMID: 11866696.
- 21Brankin V, et al. Paracrine effects of oocyte secreted factors and stem cell factor on porcine granulosa and theca cells in vitro. Reproductive biology and endocrinology : RB&E. 2003;1:55. PMID: 12941156.
- 22Nicklin LT, et al. Leptin in the bovine corpus luteum: receptor expression and effects on progesterone production. Molecular reproduction and development. 2007;74(6):724-9. PMID: 17154301.
The IGF-1 LR3 Report · $19
Everything you need to start.
Dose, sourcing, safety, our verdict. One purchase. Yours forever.
Built from 22 cited studies.
Or get every report. All reports — $99 once · Pro — $29/mo.
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